I have seen a fair number of these old guys over the years. I have alway had a question about them, which perhaps someone might be able to answer. I have seen some of these pots with long leads extending from the insulators on the HV and LV sides, and I have also seen very short leads (usually from the LV side only), with splices made to additional conductors. Question; were these transformers manufactured with long leads permanently connected to the internal windings and then brought out through the insulators, or were there connector terminals inside where conductors could be attached and brought out?

In any event, those porcelain brown or white insulators are a treasure.

Question; were these transformers manufactured with long leads permanently connected to the internal windings and then brought out through the insulators, or were there connector terminals inside where conductors could be attached and brought out?

Hi,

I've seen some pictures and drawings in old electrical books of transformer connections of these old units. From what I can tell, These old transformers had terminal blocks inside where taps could be reconnected / relinked for different primary voltages and one was able to connect the secondary for either series or parallel or series with a tap for the neutral for supplying a 120/240 volt service. Leads were already preattached to the terminals, as portrayed in an old advertisement for GE I seen once. I would assume that these connections would have been modified (If needed)either at the factory, or at the POCO's shop, and not on the job. Even in modern times this fact can probably account for the short leads that you (and I) have seen. I have seen them mainly when you can tell that there had been some work done on the secondary, such as being upgraded to triplex or such. It would obviously be much easier to splice and not open up the pot.

Regarding the picture, I don't see any primary cutout. That seems odd, because the transformer does not appear to be self protected. I'm just guessing, but just based on the size of the primary bushings and insulator on the pole, I'd say this transformer is on a 7,200 V line. (Probably rated 6,600 V)Almost all of these old transformers I seen were connected to 2400 V lines (either 4160Y/2400 or 2400 delta)

Yes, the old distribution transformers had pigtail leads that were continuous from inside the "can" to the outside. They passed through hollow porcelain bushings, and the space between the bushing and the conductor was sealed with something called "compound" (a mysterious substance which had myriad uses in 20th-century electrical practice).

I believe the overhanging top of the can (a "signature" of Westinghouse transformers, though other brands may have had it as well) was intended to shield the bushings from rain.

The POCO xfrs here (NJ) were tagged 'NO-PCB's' for 'clean' ones; and all the non-clean ones were swapped out.

The oil within many if not most OLD transformers contained PCB's (Polyclorinated bi-phenyls). That is a controlled hazardous item, which has caused large amount of pollution/contamination.

It was used a lot in xfr oil, and OLD magnetic ballasts. The 'newer" mag ballasts were marked "no PCB's" or "Non-PCB"

Large xfrs were 'treated/flushed' and refilled with non-PCB oil. This process did not totally eliminate the PCB contamination, it lowered the 'count' to levels acceptable to the US EPA/DEP standards.

'Old' ballasts that contained PCB's were treated as regulated hazardous waste, and required packaging into a steel drum, sealable lid, and a LOT of EPA/DEP documentation. Needless to say, this was and still is a expensive proposition to dispose of legally.

I had (customer owned) 9 'mat' setup 500Kva xfrs 'cleaned', and 3-750Kva that had to be 'disposed'. The 3x750 Kva removal/documentation/disposal by a Lic Haz Waste Disposal company was in excess of $15k, back in '81.